Over the years, Clark has developed hard feelings for the Luthor's with all of the trouble that they have caused him prying into his personal life. With the revelation of Lex Luthor's clones in Cadmus Labs and Tess Mercer being Lionel Luthor's daughter, it seems that the Luthor name is slowly crawling back into Clark's life.
As Lionel Luthor's only living heir, Tess is given a relic from Krypton that transports Clark to another world where he comes face to face with a shadow. One that he never expected to lay his eyes on and up until now puts Darkseid to shame. That being Lionel Luthor himself, who is anything but dead. Clark finds himself backed into a corner when dealing with Lionel, while also learning about his alternate half Clark Luthor,a relentless murderer who was raised by Lionel and transported to his world.
While previous episodes of this season mention Clark's dark side, this is the episode where we finally see a manifestation of it. While Clark has shown to be ruthless in the past (due to Red K) he has never been evil. Through Clark Luthor, allegations of Clark's darkness become facts that his loved one's can no longer simply ignore.
And who better to bring that side out of him then the same man that drove Lex to the Darkside. While Darkseid himself may be the embodiment of evil, his overall effect on Clark doesn't hold a candle to Lionel Luthor's. Through Lionel, Clark learns about his life and choices that he made in this world and even gains insight as to why Lex Luthor, once his best friend turned to evil. He also faces his worst fear of Lois Lane truly hating him. Most importantly, Clark finally understands just how easy it can be for someone to be corrupted when there is no light to guide them.
I think this is the best episode of this season, and definitely one of the best episode's in the entire series. The best part being of course the return of Lionel Luthor. John Glover proves that despite being gone for 3 years, he has not lost a step which makes his return all the more exciting. The biggest surprise for me was how impressed I was with Tom Welling's acting. His portrayal of Clark Luthor was creepy and vile, something I would have never expected him to pull off, and so expertly too. I love what they did with the alternative world too. The colder colour tones made it look like your were seeing into the negative side of a film or photograph.
I won't give the ending away with this one, but I will personally give it a 10 out of 10.